The invention relates to a steam turbine and more particularly to an improved Curtis blade ring and inner cylinder interface.
In steam turbines with a circumferential tongue supporting the Curtis stage blade ring, steam flows through ports in the tongue and when operating in a load following mode the steam temperature varies from 750.degree. F. at partial load to about 950.degree. F. at full load. The temperature of the heavy inner cylinder wall remains substantially lower constraining expansion of the tongue resulting in high magnitude compressive stresses in the tongue and plastic deformation. These strains are reversed when the turbine is taken off the line and cools leading to eventual thermal fatigue and cracking of the tongue.